Method of and apparatus for correcting tubing eccentricity by drawing



June 25, 1963 HELBLE c. ETAL 3,095,083 moo OF AND APPARATUS FOR coamscwmc mama ECCENTRICITY BY muwmc Filed Nov. 3. 195B 6 Sheets-Sheet 1 IIIII/I/II.

FIG.1

IN VENTORS CHALMERS L. HELBLE BY FRANK LBOYER M ATTORNEY J ne 25. 1963 c. L. HELBLE ETAL 3,095,933

METHOD 0? AND APPARATUS FOR CORRECTING TUBING ECCENTRICITY BY DRAWING Filed Nov. 5, 1958 6 Sheets-Sheet 2 FIG.4

INVENTORS CHALMERS L.HELBLE FRANK LBOYER m ATTORNEY June 25, 1963 C. L. HELBLE ET METHOD OF AND APPARATUS FOR CORRECTING TUBING ECCENTRICI'I'Y BY DRAWING Filed Nov. 3, 1958 6 Sheets-Sheet 3 ATTORNEY June 25, 1963 c. HELBLE ETAL 3,095,033

METHOD 0F AND APPARATUS FOR CORRECTING TUBING ECCENTRICITY BY DRAWING FRANK L BUYER ATTORNEY June 25, 1963 c L HELBLE ETAL 3,095,083

METHOD OF AND AP PARATUS FOR CORRECTING TUBING ECCENTRICITY BY DRAWING Filed Nov. 3, 1958 6 Sheets-Sheet 5 FIG.1O

INVENTORS CHALMERS L. HELBLE FRANK L. BOYER ATTORNEY United States Patent Oflice 3,095,083 APPARATUS FOR CORRECT- [NG TUBING ECCENTRICITY BY DRAWING Chalmers L. Helble, New Brighton, and Frank L. Boyer, Beaver Falls, Pa., assignors to The Bahcock & Wilcox Company, New York, N.Y., a corporation of New Jersey Filed Nov. 3, 1958, Ser. No. 771,642 7 Claims. (Cl. 205-4} This invention relates to the manufacture of metal tubing and, more particularly, to a novel method of and tubing of uniform Wall thickness.

In the manufacture of metal tubing, particularly seamless tubing, manufactured by the rotary piercing or extruexample, there is usually a lack of conthe inner and outer circular peripheries of the tubing resulting in a variation in the wall thickness of the tubing circumferentially thereof. The zones of maximum and minimum wall thickness are substantially diametrically opposite each other. In the case of eccentric extruded tubing, the zone of maximum wall thickness generally extends substantially longitudinally of whereas, While in the case of rotary pierced tubing, such zone tends to follow a spiral path along the tubing.

For many applications of tubing, such variation in wall thickness is not an important factor. However, certain applications require tubing having not less than a preset minimum wall thickness. When the inner and outer form oircumferentially of the tube.

Stated succinctly, to obtain a pre-set minimum wall thickness in a tube whose Wall thickness varies circumferentially requires a greater amount of metal than is needed to obtain the same pre-set minimum wall thickness in a tube whose wall thickness As a result, the material cost of such a tube having a variable wall thickness exceeds that of a tube having a uniform wall thickness. This is an excess metal cost which can run into a large sum in mass production of tubing. Consequently, there is a substantial saving in metal cost available in producing tubes with a pre-set minimum wall thickness if the tube can be produced with a uniform wall thickness, as less' weight of metal would be required for each such tube.

ferential periphery One form of apparatus for performing this operation comprises an annular size reducing die having a frusto- 3,095,083 Patented June 25, 1963 However, the method may its axis parallel to the line of draw but of such are. using a die having having an inlet centered on the line of thinnest wall.

Preferably, the adjustments of the tilting die are effected by power actuators remotely controlled by an operwall thickness tube marked at crrcurnferentially spaced the invention; view of FIG. 4; FIG. 1 illustrating a variation processed in accordance with FIG. 5 is an end elevation FIG. 6 is a view similar to of the invention method;

FIG. 7 is a part elevation and part schematic view of the mounting and adjusting means for a tilting die and the control therefor;

FIG. 8 is a side adjusting means;

FIG. 9 is a front elevation view of the control unit for the die adjusting means;

FIG. 10 is a sectional view on the line 10-10 of FIG. 9;

FIG. 11 is a plan view of the control unit;

FIG. 12 is a side elevation view of a follow up mechanism for the adjusting means and control unit; and

FIG. 13 is a sectional view on the line l313 of FIG. 12.

elevation view of the die mounting and gerated manner.

The annular sinking die 20 has an outwardly flaring frusto-conical entrance thr-oat 21 and a similar exit throat 22, which intersect substantially midway of the axis of die 20. Preferably, the included angle of throat 21 is of the order of 30 degrees.

In a manner described more fully hereinafter, die 20 is mounted for tilting about one of its diameters as an axis, and the tilting may be varied through an angle of the order of degrees. Furthermore, die is arranged for rotational adjustment of its point of maximum tilt about the die axis through 361) degrees. Thus, the die may be tilted an amount determined by the degree of metal displacement required in tube 10 and its point or are of maximum tilt may be rotated to remain in line with the line of minimum wall thickness. As stated, this line may run rectilinearly of tube 10 or may spiral therealong.

Die 20, being a sinking die, reduces the outer diameter of tube 10. By virtue of the tilting of die 20 relative to the axis of tube 10, the reducing action of die 20 can be selectively applied to a selected are of the periphery of tube 10, with the remaining portion of the periphery being reduced more lightly or not at all. At the extreme tilt position of die 20 as shown in FIG. 1, the surface of entrance throat 21 is substantially parallel to the outer surface 12 of tube 10 along the arc of the thicker wall portion 14.

However, over the are including the thinner wall portion 13, greater radial unit pressures are exerted on the metal of the tube wall, so that the metal is crowded circumferentially of tube 10 by virtue of the reducing action of die 20. This displaced metal, flowing circumferentially of tube 10, increases the thickness of the tube wall along the are including thin wall section 13. By proper selection of the degree of tilt with reference to the difference between the thickest and thinnest wall portions, the thickness of the thinnest wall section can be made equal to that of the thickest wall section, thus producing a drawn tube having substantially uniform wall thickness, as best shown in the large scale section of FIG. 3.

The circumferential displacement of metal as a result of such selective exertion of greater radial unit pressures over a selected are as tube 10 is drawn through die 20 is graphically illustrated in FIGS. 4 and 5. These figures depict the actual metal displacement which occurred when a tube of initially substantially uniform wall thickness was drawn through a reducing or sinking die tilted in accordance with the invention method.

In the test, the results of which are shown graphically in FIGS. 4 and 5, an electrical resistance welded (ERW) tube 30, made in the usual manner from a strip of metal of substantially uniform wall thickness, was scribed with longitudinally extending lines A, B, C, etc. at uniformly spaced intervals around its outer circumference. This tube was then drawn through a sinking die, such as die 20, tilted at an angle of 15 degrees to the axis of tube and arranged to exert greater radial unit pressures on the metal of the upper half of the tube. As will be noted from FIGS. 4 and 5, this thickened the wall of the upper part of tube 30 along a selected are. The scribed lines B, C and D were displaced circumferentially to the positions B, C, D, with substantially no circumferential displacement taking place at lines A and E. Lines B were shifted the greatest amount, line C a lesser amount, and lines D the least amount. This provided a graduated variation in thickness between thickened wall portion 31, at the top of tube 30, and unaffected wall portion 32 at the bottom of the tube.

The test graphically depicted demonstrates the circumferential displacement of the metal which has greater radial unit pressures exerted thereon by tilted die 20. Applying the same technique to the thinner wall portion of a tube of non-uniform wall thickness, with selective control of the degree of die tilting, results in circumferential displacement of the crowded metal of the thinner wall portion to thicken this wall portion in a graduated manner so that a tube of substantially uniform wall thickness is provided.

In the modified technique of FIG. 6, die 20 is maintained with its axis parallel to the axis of the tube portion on the exit side of the tube, and tube 10' is fed at a controlled angle to die 21]. This again crowds the metal of thinner wall portion 13' circumferentially to displace the metal in the selected are and thus thicken wall portion 13 to a. thickness substantially equal to that of wall portion 14'. While adequate results can be obtained by this technique, the tilted die technique of FIGS. 1, 2 and 3 is presently preferred.

FIGS. 7-13 illustrate apparatus for controllab'ly varying the degree of tilt and angular orientation of a tiltablc sinking die 20. Referring to FIGS. 7 and 8, a gimbal support 35 is provided with keys 36 for positioning of the support in a draw bench. Support 35 has diametrically opposite bearings which are horizontally coaxial and receive horizontal trunnions 41 on an outer ring 40. A bracket 37 on the upper surface of support 35 has projecting spaced and aperturcd ears 38 which receive trunnions 42 on a hydraulic actuator having a piston rod 43 carrying a fork 44 connected by a pin 46 to an arm 47 projecting forwardly from outer gimbal ring 40. Operation of actuator 45 will thus tilt outer ring 40 about a horizontal axis.

Ring 40 has diametrically opposite coaxial bearings whose common axis perpendicularly intersects the common axis of trunnions 41. The bearings of ring 40 receive coaxial diametrically opposite trunnions 51 on an inner gimbal ring 50. Ring is thus angularly dis place-able about an axis perpendicular to the axis of displacement of outer ring 40, and rings 40 and 50 conjointly provide a universal mounting for die 20. A pair of upright plates 60, at one side of support 35, have their upper ends interconnected by a shelf 61 connected to an upper shelf 62 by side plates 63. Shelves 61, 62 carry bearing caps 64 containing vertically coaxial bearings 66 receiving trunnions on a bracket having side plates 67 receiving horizontally coaxial trunnions 56 on a hydraulic actuator 55 having a piston rod 57. Actuator 55 thus has freedom of movement about a pair of mutually perpendicular axes.

Inner gimbal ring 50 has convex upper and lower outer edges and has a forwardly extending frusto-conical lead-in section 52 merging with a frusto-conical and shouldered seating recess 53 for die 20. A flared exit passage 54 extends from the inner or trailing end of recess 53 and may merge with exit section 22 of die 20. Ring 50 is operably connected to actuator 55 by means of an arm 58 on the outer edge of section 52 having a hemispherical recess receiving a spherical outer end of piston rod 57. A spherically concave nut holds such end in the recess. By this connecting means, ring 50 may be pivoted about an axis perpendicular to the pivot axis of ring 40.

Adjustment of the degree and direction of tilt of die 20 in its gimbal mounting 3S-40-50 is effected by a gimbal controller 70 mounted on a base or column 71 and including a control handle 75. Referring to FIGS. 9 to ll, controller 70 includes a generally tubular housing body 72 to the outer end of whiuh is secured an L-shaped ring 73. About midway of the length of body 72, is disposed an annular ring 74 having diametrically opposite trunnions 76 engaged in apertures in the body 72. A circular plate 77 is concentric and, in the neutral position coplanar, with ring 74 and has diametrically opposite trunnions 78 engaged in the latter. The axis of trunnions 73 is perpendicular to that of trunnions '76.

Ring 73 seats axially spaced antifriction bearing races 81 held in position by a lock ring 82 threaded into ring 73. These races rotatably support a slide guide having a flat annular rim 83 seated between the bearing races. A convex guide element 84 extends diametrically of rim 83 and its arc is concentric with the axis of trunnions 78. Element 80 has a rectangular slot 86 formed with guide rails 87, along its longer edges, on which is mounted an arcuate slide 85. Slide 85 has a central aperture through which extends a control rod 90 which also extends centraily through plate 77 and is secured thereto by a nut 88. Nut and washer assemblies 91 secure rod 90 to slide 85, and control handle 75 is pinned to the outer end of the rod.

Scales 92 are marked along element 84 on each side of slot 86 and extending through 15 degrees, for example, to each side of the midpoint of the element. A dial ring 93, graduated through 360 degrees, is secured to the outer end of ring 73 and cooperates with a pointer 94 on guide 80. Handle 75 extends longitudinally of element 84 and is aligned with pointer 94.

With the rigid connection of rod 90 to handle 94, slide 85, and plate 77, the latter may be tilted through 15 degrees, for example, in either direction and at any angular position around ring 93. At the 90 degree and 270 degree position shown in FIG. 9, if handle 75 is moved in either direction, plate 77 will be tilted about its trunnions 78 and ring 74 will remain stationary. At the zero and 180 degree positions of handle 75, both ring 74 and plate 77 will be tilted in coplanar relation about the trunnions 76 of ring 74. In any other position of handle 75, ring 74 will be titled about trunnions 76 and plate 77 will be simultaneously tilted about trunni-ons 78, so that the effective tilting direction of plate 77 will correspond to the angular direction indicated on ring 93 by pointer 94.

Motion of handle 75 is communicated to die 20 by servo mechanism interconnecting ring 74, plate 77, gimbal rings 40 and 50, and actuators 45 and 55. Referring to FIG. 7, a motor 95 drives a pump 96 having an inlet connected to tank 97 and delivering fluid under pressure to hydraulic fluid supply lines 101 and 106 connected to fourway control valves 100 and 165, respectively. Relief valves 98 are interposed in lines 101, 106 and have overflows leading to tank 97. Valves 100, 105 are also pro vided with return lines to tank 97 as schematically indicated at 102, 107. Lines 103 connect valve 100 to actuator 45, and lines 108 connect valve 105 to actuator 55.

Valve 109 is arranged to be controlled by tilting movethe latter and on a diameter of plate 77 perpendicular to the axis of trunnions 78. Sheath 117 of cable 115 is anchored to an arched bracket 118 secured at each end to ring 74 and extending over plate 77. The other end of cable 115 is connected through linkage 12%, identical to linkage 120, to stem 109 of valve 105.

The linkages 120, 120' are connected to outer and inner gimbal rings 40 and 50, respectively, by flexible cables 121, 121' respectively. Sheath 122 of cable 121 is anchored to a bracket 123 on gimbal mounting 35, and cable 121 is connected to a forwardly projecting arm 124 on outer ring 40. Similarly, sheath 122 of cable 121 is anchored to a bracket 123 on outer gimbal ring 40, and cable 121' is connected to a forwardly projecting arm 124' on inner gimbal ring 50. These arrangements constitute follow-up connections whereby valves 100, 105 are restored to the neutral position whenever the degrees of tilt of rings 40 or 50 coincide with those of ring 74 and plate 77.

Linkage 120, which is identical with linkage 120', is best illustrated in FIGS. 7, l2 and 13. Valve 100 and linkage 120 are supported on a mounting plate 125 posi- 75 tioned in control column 71. A pair of spaced arms 126 extending normal to plate 125 support a guide 127 for a slide 130. Control cable 110 is connected to the outer end of a link 128 having its inner end pivoted on cars 131 on plate 125. A longer link 132 has its inner end pivoted on cars 133 on slide 130, and its outer end is pivotally connected by link 134 and yoke 136 to the end of valve stem 104. A short link 137, parallel and relatively close to link 134, interconnects links 128 and 132. Cable 121 is secured at the pivotal connection of link 132 to cars 133 and thus acts directly on slide 130.

In the described linkage, movement of cable 110, responsive to turning of handle 75 to a set position on dial 93 and movement along guide 80, which latter movement then results in tilting of ring 74, swings link or lever 128 about its pivot on cars 131, and thus moves valve stem I04. Valve 100 thereupon supplies hydraulic fluid under pressure to actuator to tilt outer gimbal ring 40 in the same direction as ring 74 has been tilted. As ring 40 moves toward the preset position, cable 121 moves slide 130. With link 128 fixed, thus fixing link 137, link 132 is pivoted about its connection with link 137. This moveacts in the same manner upon tilting of plate 77 by movement of control handle 75 along guide 80.

From the foregoing description, it will be seen that turning and tilting of control handle 75 results in a corresponding tilting of rings 40 and to tilt die 20 the required degree in the required direction. Thus, the openator at control handle can continuously control the direction and degree of tilt of die 20 to effect the circumferential crowding of the tube wall metal in line with the line of thinnest wall section of the tube.

It will thus be seen that a method has been provided for controllably displacing tube wall metal, during a sink ing or reducing draw operation, in such a manner as to thicken the thinner parts of the tube wall so as to provide controlled manner to insure application of the meta-1 displacement forces along the center of the arc of minimum tube Wall thickness.

entering tube axes, to crowd metal of the tube wall, within such selected arc, circumferentially of the tube to increase the tube wall thickness within said selected arc.

ter; and, during such drawing, selectively tilting the die so that the die axis intersects the axis of the tube entering the die at an angle proportional to such pre-selected amount to exert on the tube wall within said selected arc a radial unit pressure greater than that exerted on the remaining portion oft he tube circumference by virtue of the angular relation of the die and entering tube axes, to crowd metal of the tube wall, within such selected arc, circumferentially of the tube to increase the tube wall thickness within said selected are; the radial unit pressure decreasing from a maximum at the midpoint of the arc to substantially zero at the ends of the arc, and the increase in wall thickness decreasing from a maximum at the midpoint of the are to substantially zero at the ends of the are.

3. A method of processing a thickness varying circumferentially from a maximum to a minimum, comprising the steps of drawing the tube through an annular reducing die to reduce the tube diameter; and while so drawing the tube, maintaining the die oriented with its axis at an angle to the axis of the tube portion entering the die to exert on the tube wall within a selected arc, substantially centered metal tube having a wall relative to the zone of minimum wall thickness, a radial unit pressure greater than that exerted on the remaining portion of the tube circumference by virtue of the angular relation of the die and entering tube portion axes, to crowd metal of the tube wall circumferentially of the tube to increase the tube wall thickness within said selected arc.

4, A method of processing a metal tube having a wall thickness varying circumferentially from a maximum to a minimum, comprising the steps of drawing the tube through an annular reducing die to reduce the tube diameter; while so drawing the tube, maintaining the die oriented with its axis at an angle to the axis of the tube entering the die to exert on the tube wall within a selected arc, substantially centered relative to the zone of minimum wall thickness, a radial unit pressure greater than that exerted on the remaining portion of the tube circumference by virtue of the angular relation of the die and entering tube axes, to crowd metal of the tube wall, within such selected arc, to flow circumferentially of the within said selected arc; and maintaining the angle between the die and entering tube axis at a value coordinated with the maximum wall thicknesses to increase the wall thickness within such selected are to substantially such maximum thickness.

5. Apparatus for processing a metal tube having a wall thickness varying circumferentially from a maximum to a minimum; said apparatus comprising, in combination, a draw bench including a gimbal support; an outer gimbal ring mounted in said support for oscillation about a first axis; an inner gimbal ring mounted in said outer gimbal ring for oscillation about a second axis perpendicular to said first axis; an annular die having a flared entry throat mounted in said inner gimbal ring for adjustment, by oscillation of said gimbal rings about their respective axes, of the angle between the axis of said die and the axis of a tube drawn therethrough to exert on the tube wall within a selected are substantially centered relative to the zone of minimum wall thickness a radial unit pressure greater than that exerted on the remaining portion of the tube circumference, by virtue of the angular relation of the die and entering tube axes to increase the tube wall thickness within said selected are and of the position of such selected are circumferentially of the tube wall to maintain the selected are centered on the zone of minimum wall thickness; a control stand having a control handle movable about a pair of mutually perpendicular axes; and servo means interconnecting said handle and said gimbal rings to maintain the orientation of said die in correspondence with the orientation of said handle and comprising a pair of fluid pressure actuators each operatively interconnected to one of said gimbal rings, and valve selectively operable to sup- 5,; ply pressure fluid to said actuators, said valves being operatively connected to said control handle.

6. Apparatus for processing a metal tube having a wall thickness varying circumfcrentially from a maximum to a minimum; said apparatus comprising, in combination, a draw bench including a gimbal support; an outer gimbal ring mounted in said support for oscillation about a. first axis; an inner gimbal ring mounted in said gimbal ring for oscillation about a second axis perpendicular to said first axis; an annular die having a flared entry throat mounted in said inner gimbal ring for adjustment, by oscillation of said gimbal rings about their respective axes, of the angle between the axis of said die and the axis of a tube drawn therethrough to exert on the tube wall within a selected are substantially centered relative to the zone of minimum wall thickness a radial unit pressure greater than that exerted on the remaining portion of the tube circumference, by virtue of the angular relation of the die and entering tube axes to increase the tube wall thickness within said selected are, and of the position of such selected arc circumferentially of the tube wall to maintain the selected are centered on the zone of minimum wall thickness; a control stand having a control handle movable about a pair of mutually perpendicular axes; servo means interconnecting said handle and said gimbal rings to maintain the orientation of said die in correspondence with the orientation of said handle and comprising a pair of fluid pressure actuators each operatively interconnected to one of said gimbal rings, valves selectively operable to supply pressure fluid to said actuators, said valves being operatively connected to said control handle and normally having a neutral position locking said actuators against movement; and feedback linkage interconnecting said gimbal rings and said valves and operable to restore said valves to said neutral position when the orientation of said die corresponds with the orientation of said handle.

7. A method of correcting the eccentricity of a metal tube of circular cross-section having a wall thickness varying circumferentially from a maximum to a minimum, comprising the steps of drawing said tube through a die having a die orifice smaller than the diameter of the entering tube portion to reduce the outside diameter of the tube by efiecting flow of the tube metal longitudinally of the tube; and mechanically subjecting the tube portion as it enters and passes through said die orifice to an inward radial unit pressure on a selected are centered relative to the zone of minimum wall thickness greater than the inward radial unit pressure exerted on the remaining portion of the tube circumference to effect a flow of tube metal circumferentially of the tube to thereby increase the tube wall thickness within the selected are.

References Cited in the file of this patent UNITED STATES PATENTS 1,225,788 Dies May 15, 1917 1,694,477 Long Dec. 11, 1928 1,962,510 Kellog June 12, 1934 2,245,320 Bletso June 10, 1941 2,279,174 Morgan Apr. 7, 1942 2,368,628 Bates Feb. 6, 1945 2,379,778 Allen July 3, 1945 2,526,237 Johnson Oct. 17, 1950 2,602,539 See July 8, 1952 2,928,526 Kerr Mar. 15, 1960 FOREIGN PATENTS 22,758 Great Britain Oct. 14, 1896 542,002 Germany Jan. 18, 1932 518,723 Italy Mar. 8, 1955 449,571 Great Britain June 28, 1948 301,876 Switzerland Dec. 1, 1954 155,629 Australia Mar. 10, 1954 592,837 Great Britain Sept. 30, 1947 

1. A METHOD OF INCREASING BY A PRE-SELECTED MAXIMUM AMOUNT THE WALL THICKNESS OF A METAL TUBE THROUGH A SELECTED ARC OF THE TUBE CIRCUMFRENCE, COMPRISING THE STEPS OF DRAWING THE TUBE THROUGH AN ANNULAR REDUCING DIE, HAVING A FLARED ENTRY THROAT, TO REDUCE THE TUBE DIAMETER; AND, DURING SUCH DRAWING, SELECTIVELY TILTING THE DIE SO THAT THE DIE AXIS INTERSECTS THE AXIS OF THE TUBE ENTERING THE DIE AT AN ANGLE PROPORTIONAL TO SUCH PRE-SELECTED AMOUNT TO EXERT ON THE TUBE WALL WITHIN SAID SELECTED ARC A RADIAL UNIT PRESSURE GREATER THAN THAT EXERTED ON THE REMAINING PORTION OF THE TUBE CIRCUMFRENCE, BY VIRTUE OF THE ANGULAR RELATION OF THE FLARED ENTRY THROAT AND ENTERING TUBE AXES, TO CROWD METAL OF THE TUBE WALL, WITHIN SUCH SELECTED ARC, CIRCUMFERENTIALLY OF THE TUBE TO INCREASE THE TUBE WALL THICKNESS WITHIN SAID SELECTED ARC. 